LIGHT. 1 1 1 



upon the rotator, they can be made to slide by each 

 other so as to expose a greater or less angle of any 

 color. By using any two or more of these at a time, 

 many interesting effects from combined colors can be 

 exhibited. 



One may often find colored stars or rings or other 

 fanciful designs on posters for advertisements or wrap- 

 pings on goods of various sorts, which may be utilized 

 with the rotator in studying color. 



FRAUNHOFER'S LINES. 



The solar spectrum as usually projected with around 

 orifice and common prism, with an included angle of 

 60, appears complete, and is often called a pure spec- 

 trum. If, however, the prism be of flint-glass or, better 

 still, a bottle prism filled with bisulphide of carbon, it 

 may be placed in such a position as to present the 

 absorption lines known as Fraunhofer's. 



Fiff. SS. 



To do this it will only be necessary to place the 

 prism in the full beam from the porte lumicre and turn 

 it so that one side is very nearly parallel with the beam. 

 A spectrum will be formed containing a number of 

 dark perpendicular lines known as the C D E F and 

 G lines. These may be still more marked by placing 



